Connector plate

ABSTRACT

The connector plate has a plurality of slender nail-like teeth struck to project at right angles to the plate for embedment into adjoining wooden members. The teeth are struck in longitudinal rows with the teeth in each row being staggered longitudinally relative to the teeth of next adjacent rows. The teeth in every second alternate row are struck such that the slots left thereby in the plate extend from the teeth in like directions while the teeth in the next adjacent alternate row in are struck such that the slots left thereby in the plate extend an opposed longitudinal direction to the slots formed in adjacent alternate rows. The teeth in the rows between such alternate rows are formed in longitudinally spaced pairs with each pair of teeth struck to jointly define a slot in the plate, the teeth being located at opposite ends of the slot. These paired teeth are shorter in length than the length of the teeth in adjacent rows and are twisted about their longitudinal axes when struck whereby increased resistance to withdrawal is effected. These short teeth have oppositely scarfed tips to provide a clinching action upon embedment into the wooden members. The tips of the longer teeth in the alternate rows are chisel-pointed providing optimum penetration characteristics upon embedment.

The present invention relates to metal connector plates and structuralwood joints formed thereby and more particularly to connector plates andjoints of the butt-type useful in prefabricated wooden structures suchas roof trusses and the like, and further represents an improvement tothe connector plate structure as illustrated in Jureit U.S. Pat. No.3,892,160.

The joinder of structural load bearing wooden members has recently andsignificantly been advanced with the advent of structural wooden jointswhich are connected solely by means of metal plates having slenderelongated nail-like teeth struck therefrom and embedded into the woodenmembers, such as illustrated in Jureit U.S. Pat. No. 2,877,520. Platesof this type wherein the teeth serve as the only means holding theplates onto the wooden members and the wooden members in adjoiningrelation and the joints formed thereby have proved eminently successfulparticularly in the building industry. Various arrangements andconfigurations of teeth in the plates have been proposed and constructedin the past for specified purposes and to solve particular problemsassociated with utilization of connector plates of this type inspecified woods.

Prior connector plates have utilized single teeth struck in longitudinalrows, with the teeth in each row being staggered relative to the teethof next adjacent rows such that the slots in next adjacent rows extendfrom the teeth in opposite directions, such as illustrated in JureitU.S. Pat. Nos. 3,390,902; 3,731,583, and 3,910,153. The presentinvention provides an improved connector plate wherein rows of pairedteeth are located between alternating rows of single teeth.

The present invention provides a connector plate which is particularlyuseful in soft woods, for example Norweigian spruce. It has been foundthat when conventional connector plates of the foregoing noted type,particularly wherein the teeth are substantially all the same length,are applied to soft wood, the joint fails in tension. That is to say,when the butting wooden members are placed under tensile stresses, theteeth have a tendency to compress the soft wood behind them with theresult that the teeth force the formation of significantly largeropenings or holes in the wood. The openings in the wood, in effect,spread or enlarge and permit the teeth to bend and slide from theopenings. Once the openings for the teeth are enlarged, the resistanceto withdrawal of the teeth from the wooden member is significantlydecreased with the result that the teeth pull out and the joint fails intension. It has thus been a problem to effectively employ connectorplates of the type having integrally struck teeth projecting to one sidethereof in joints wherein the wooden members of the joint are formed ofthe generally softer woods.

The present invention provides a connector plate which eliminates and/orminimizes the foregoing and other problems associated with priorconnector plates and provides a novel and improved connector platehaving various advantages in construction, mode of application andresult and particularly useful for joining wooden members formed of thesofter woods. Particularly, the present invention provides a connectorplate having a plurality of slender nail-like teeth struck integrally toproject to one side of the plate. The teeth are formed in longitudinallyextending rows with the teeth in each row being staggered relative tothe teeth of the next adjacent rows. The teeth in every second alternaterow are struck such that the slots left thereby in the plate extend fromthe teeth in like directions while the teeth in the next adjacentalternate row are struck such that the slots left thereby in the plateextend in an opposed longitudinal direction to the slots formed inadjacent alternate rows. The teeth in the rows between the alternaterows thereof are struck in pairs such that a single slot is left in theplate by each such pair, the paired teeth being located at opposite endsof such slot. These latter teeth are hereinafter referred to as doubleor paired teeth. Each set of paired teeth are laterally adjacent asingle tooth whereby the number of paired teeth in each row thereof issubstantially twice the number of the teeth in each adjacent rowcontaining the single teeth. The paired teeth are thus slightly greaterthan one half the length of the single teeth. The paired teeth aretwisted about their longitudinal axes when struck and thereby effectincreased resistance to withdrawal when embedded into a wooden member.These paired teeth are also provided with oppositely scarfed tipswhereby the teeth are deflected laterally upon embedment into the woodenmembers to clinch the wood strands. The tips of the single teeth arechisel-pointed for optimum penetration characteristics.

A plate constructed as described in the previous paragraph providesincreased resistance to tensile forces when applied to the joint formedby two butted wooden members, particularly wherein the wooden membersare formed of soft wood. The double teeth in essence take the place of asingle tooth and thus provide increased surface area against which thewood bears when the joint is subjected to tensile forces. That is, thecritical area at which the tooth tends to enlarge the hole in the woodenmembers is close to the base of the tooth. By providing a substantialincrease in the number of the teeth and hence areas of the teeth againstwhich the wood bears particularly at the bases of the teeth, increasedresistance to hole enlargement is provided. Also, by providing pairedsets of short teeth uniformly distributed throughout the plate anddistributed uniformly among the longer single teeth, the resistance towithdrawal of the teeth from the wooden members is significantlyincreased particularly at the initial stages of any tendency of theteeth to withdraw. That is, the teeth have optimum or maximum withdrawalresistance when fully embedded. Conversely, the insertion pressurerequired at the beginning of a press stroke to embed the teeth into thewooden members is initially small with such insertion pressureincreasing near the end of the stroke. Consequently, initial toothpenetration is facilitated while accurate location of the plate relativeto the joint is assured. Also, the effectiveness of each tooth in thejoint is assured by the plate hereof due to the foregoing penetrationcharacteristics. That is, bending of the teeth upon insertion, exceptwhen a clinching action is achieved by the paired teeth, issubstantially eliminated.

The twisting of the paired teeth when initially struck also increasesthe resistance to withdrawal of the paired teeth from the wooden member.The generally corkscrew twist of the paired teeth requires removal ofadditional wood fibers from the wooden member in order to withdraw suchpaired teeth from the wooden member whereby increased holding power isachieved.

Accordingly, it is a primary object of the present invention to providea novel and improved connector plate and joint formed thereby.

It is another object of the present invention to provide a novel andimproved connector plate particularly useful for joining butted membersformed of soft woods.

It is still another object of the present invention to provide a noveland improved connector plate and joint formed thereby wherein thestrength of the joint in tension is substantially increased.

It is a further object of the present invention to provide a novel andimproved connector plate and joint formed thereby wherein optimumresistance to withdrawal of the plate from the wooden member is providedwhen the teeth are fully embedded in the wooden members.

It is still a further object of the present invention to provide a noveland improved connector plate and joint formed thereby wherein the platehas an increased number of teeth per square inch.

These and further objects and advantages of the present invention willbecome more apparent upon reference to the following specification,appended claims and drawings wherein:

FIG. 1 is a fragmentary plan view of a connector plate constructed inaccordance with the present invention viewing the plate from the side towhich the teeth project and from within the wooden members of the jointformed thereby;

FIG. 2 is a cross-sectional view thereof taken about on lines 2--2 inFIG. 1; and

FIG. 3 is a cross-sectional view thereof taken about on lines 3--3 inFIG. 1.

Referring now to the drawings, particularly to FIG. 1, there isillustrated a plate generally designated 10 constructed in accordancewith the present invention and illustrated on one side of a pair ofwooden members 12 and 14. It will be appreciated that a pair of suchplates 10 are provided on the opposite sides of butted wooden members 12and 14 with the teeth thereof penetrating the wooden members toward oneanother whereby a secure butt joint between the wooden members isformed. Plate 10 is provided with first and second alternatelongitudinally extending rows of teeth designated A and C, respectively.The teeth 16a and 16c, of rows A and C, are of like configuration andare struck such that the slots 18a of rows A extend in oppositedirections to the slots 18c of row C. Teeth 16a lie in transversealignment one with the other across the plate. Teeth 16c also lie intransverse alignment one with the other across the plate. As bestillustrated in FIG. 3, the teeth 16a and 16c are provided withchisel-pointed tips 19 to optimize their penetration into the woodenmembers and also have a generally shallow V-shape in cross-sectionwhereby increased column strength is provided. Rows of teeth designatedB lie between alternate rows A and C of teeth 16a and 16c, and providelongitudinally spaced teeth 20 and 22 struck in longitudinally spacedpairs thereof. That is, the teeth in each row B are struck to providelongitudinally spaced pairs or doublets of teeth 20 and 22. Each pair ofteeth 20 and 22 are struck from the plate to leave a single slot 24 inthe plate with the teeth 20 and 22 lying at respective opposite ends ofthe slot. As best illustrated in FIG. 3, teeth 20 and 22 are struck withtips oppositely scarfed as indicated at 26 and 28 respectively toprovide a clinch action upon embedment into a wooden member.

Teeth 20 and 22 are twisted when struck to form a corkscrewconfiguration of limited axial extent. As illustrated in FIG. 1, theteeth 20 and 22 are twisted in a like direction generally not more thanabout 45 degrees from their bases to their tips. Also, the teeth 20 and22 are grooved longitudinally along the base portions thereof whereby agenerally shallow V-shaped configuration in cross-section is obtained.The twisting action blends one side of the tooth with the other adjacentthe tip portion such that the shallow V-groove widens to the extent thatthe tooth tip portion in cross-section is generally rectilinear. Theshallow V-groove is provided for increased column strength. The twistingof teeth 20 and 22, as noted previously, provides increased resistanceto withdrawal from the wooden member.

In a preferred form of the plate hereon, the longitudinally extendingrows of teeth defined in rows, A, B and C lie on centers equispaced onefrom the other across the plate, and particularly centers 0.28125 inchesapart as indicated by the dimension "a" with the centerline of the rowsadjacent the margin of the plate lying 0.1406 inch from the edge of theplate. The teeth in the rows designated A and C are spaced back-to-back0.782 inches one from the other as indicated at "b" and have a length"c" (FIG. 3) of 0.5505 inches from their tips to the underface of theplate. The spacing "d" between the opposing faces of the doublets orteeth 20 or 22 is 0.488 inches. The length "e" of the teeth 20 or 22from the face of the plate to the tips of 0.312 inches, the tips beingscarfed at 45° angles. The distance between the edges of the slots inadjacent rows indicated at "f" is 0.1562 inches. The distance betweenthe front face of a tooth 16 and rows A and C and the center of a frontface of a tooth 22 in the next adjacent row indicated at "g" in FIG. 1is 0.5313 inches. The distance h between the front face of tooth 22 andthe front face of tooth 16 in the next adjacent row is 0.2507. Eachtooth has a width of 0.125 inch. The plate is preferably formed ofU.S.S. 18 Gauge galvanized sheet metal having a thickness of 0.0516inch. The arrangement of teeth disclosed has approximately 6.8 teeth persquare inch.

The foregoing described plate has particularly high resistance towithdrawal in the soft woods. This is in part due to the large number ofteeth per square inch in the plate and due to the large frontal areapresented by the teeth at their base to the wood when subjected totensile forces.

It will also be appreciated that the teeth in the rows indicated Crespectively lie substantially medially between the teeth comprising thesets of teeth in laterally next adjacent rows B while the teeth in rowsA lie substantially medially between the spaced pairs in order to avoidcutting the wood fibers between the teeth of adjacent rows. Futher, theratio of the length of the teeth in row B to the length of the teeth inrows A and C is (0.312/0.5505) or 0.566 and it has been found that suchratio should be maintained within a range of about 0.5 to 0.7 in orderto optimize withdrawal resistance as well as facilitate penetration ofthe teeth into the wooden members. The invention may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof. The present embodiment is therefore to beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims ratherthan by the foregoing description, and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:
 1. A connector plate for joining members in abuttingrelationship comprising: an elongated plate, a plurality of elongatedprojecting nail-like teeth struck from said plate thereby leaving aplurality of slots in said plate, said teeth projecting from one side ofsaid plate, said teeth being struck in longitudinally extendinggenerally parallel rows, the teeth in first alternate rows being strucksuch that the slots left thereby in said plate extend from the teeth inlike longitudinal directions, the teeth in second alternate rows beingstruck such that the slots left thereby in the plate extend from theteeth in opposed direction to said slots formed in said first alternaterows, a row of teeth between each of said first and second alternaterows with the teeth therein being struck to form a plurality of sets oflongitudinally spaced pairs of teeth, the teeth in each set being strucksuch that a continuous slot is left in said plate between said teeth ineach set with the portions of the slot left by each tooth of each setextending therefrom toward the opposite tooth of each set, successiveteeth in said first alternate rows thereof being spaced longitudinallyand relative to said sets of teeth in next adjacent rows such that eachsuccessive tooth lies between each successive set of teeth, andsuccessive teeth in said second alternate row thereof being spacedlongitudinally and relative to said sets of teeth in next adjacent rowssuch that each successive tooth lies between said pairs of teeth formingsaid set.
 2. A connector plate according to claim 1 wherein said plateis formed of sheet metal.